There is known a camera calibration device for estimating camera parameters based on image information and real-space information in order to calibrate a posture of a camera. Such a camera calibration device estimates camera parameters (specifically, a rotation matrix and a translation matrix which indicate a posture of a camera) capable of conversion between 2D coordinates on an image and 3D coordinates in the real space. Exemplary camera calibration devices are described in Non-Patent Literatures 1 to 3.
The devices described in Non-Patent Literatures 1 to 3 are directed for estimating camera parameters based on reference points where a 2D coordinate on an image is associated with a 3D coordinate in the real space. At first, a piece of special calibration equipment with a known arrangement of reference points is installed in a field of view of a camera to be calibrated. The arrangement of reference points is known, and thus a positional relationship of the reference points in the real space is also known. Therefore, the above devices can acquire real-space 3D coordinates of the reference points.
Then, the camera calibration equipment is shot by the camera to be calibrated. The above devices acquire 2D coordinates on the image of the reference points from the shot image. The above devices make calculations based on projection equations thereby to estimate camera parameters by use of a correspondence between the 2D coordinates on the image of the acquired reference points and the 3D coordinates in the real space.
Non-Patent Literature 4 describes the Zhang method as an exemplary calibration method therein.